Existing microwave antennas include a wide variety of configurations for various applications, such as satellite reception, remote broadcasting, or military communication. The desirable characteristics of low cost, lightweight, low profile form factors and mass producibility are provided in general by printed circuit antennas, wherein flat conductive elements are spaced from a single essentially continuous ground element by a dielectric sheet of uniform thickness. The antenna elements are designed in a periodic or a periodic array of like elements and may be used for communication systems such as Identification of Friend/Foe (IFF) systems, Personal Communications Service (PCS) systems, satellite communications systems, and aerospace systems, which require such characteristics as low cost, lightweight, and low profile form factor.
However, when wide bandwidth and high electronic scan angles are desired, these antennas may not meet stringent requirements on efficiency over octave plus or greater bandwidths. In such cases, the use of tightly coupled antenna arrays, typically using dipole type elements, can be used to increase bandwidth at the expense of efficiency over the full scan range. Since coupling changes substantially over wide bandwidths, maintaining efficiency at all desired scan angles may not be possible. Typically one would design the array elements such that maximum efficiency is achieved in the high scan region while sacrificing efficiency on bore sight Additionally, dipole antenna elements in such phased array applications require a set height above a ground plane. Therefore another possible drawback in some of these systems is the element-to-module interconnect, such as the feed network described in U.S. Pat. No. 6,483,464, that is essentially hand-made without using automated manufacturing techniques. Any handmade feed network would require many man-hours to build the thousands required for a large antenna array, thus the cost would typically be prohibitive.
Current state of the art dual polarized antenna arrays include proximity fed patch antenna arrays that can achieve as much as 30% bandwidth. These array elements are suited for automated manufacturing, but not for operating bandwidths much in excess of 30%. Some Visalia antenna arrays have bandwidths in excess of an octave, but suffer depth and integration issues for low profile electrically scanned antenna (ESA) applications. A noncontiguous ground plane is used in some of these antennas, making this type of antenna array difficult to adapt to automated manufacturing. Other dipole array antennas have acceptable bandwidth, but employ feed networks that are not suited for low cost automated manufacturing or applicable to pick-and-place and associated surface mount technology.